1. Field of the Invention
The present invention relates to a mobile terminal constituting an ad hoc network together with a plurality of the terminals, a wireless communication system including the mobile terminal, and a mobile terminal control method for controlling the mobile terminal.
2. Description of the Related Art
An “ad hoc network” composed of a plurality of autonomous distributed mobile terminals each having a wireless communication function and a routing function, has been known. By adopting the ad hoc network, a network can be composed of only mobile terminals without depending on a base station, a backbone network and the like which are used in a wireless communication system. A secure routing technique and the like using a key exchange and management technique, access control and keys have been studied in order to achieve secure communications in the ad hoc network.
Meanwhile, methods have been disclosed as a technique for coordinating a routing process and a power supply control process with each other. In one of the methods, when a terminal receives a packet, a packet relay unit, a control unit or the like in the terminal is selectively powered on and off for the purpose of saving battery consumption, according to whether the received packet as a packet to be relayed or to be handled in the terminal itself (refer to Japanese Patent Application Publication No. 2005-303896). Moreover, another one of the methods has been disclosed. In this method, a certain route with which the costs for electric power is the lowest is selected, firstly by measuring the amount of remaining electric power at each node on a network, and then by calculating the electric power costs concerning each route from the amounts of the remaining electric powers of the respective nodes (refer to Japanese Patent Application Publication No. 2005-160062).
However, in a case of using the foregoing techniques for coordinating the routing process and the power supply control process with each other, a transmission path may sometimes be lost. This is because a user may turn on the power of a mobile terminal only when the user sends his/her own packets, and turn of the power in the other occasions. Such a selfish operation may results in a loss of a transmission path and in a trouble that another mobile terminal fails to transmit its own packets. For the reason, there has been a problem that the fairness in communications cannot be ensured because the network performance of an ad hoc network deteriorates due to such a self-serving operation by a user.